Microwave switch utilizing latched ferrimagnetic material in coupling aperture of waveguide coupler

ABSTRACT

Two rectangular waveguides are interconnected by a coupling aperture in which a ferrimagnetic body is disposed. At least one latching conductor extends through the body in the axial direction of the waveguides or in a direction perpendicular thereto. A pulse current flowing through the conductor causes a change in direction or magnitude of the magnetization of the ferrimagnetic body. This permits an electromagnetic wave, applied to either one of the input waveguide ends, to appear at that output end at which the wave did not previously appear.

United States Patent Nakahara et a].

[54] MICROWAVE SWITCH UTILIZING LATCI-IED FERRIMAGNETIC MATERIAL INCOUPLING APERTURE OF WAVEGUIDE COUPLER [72] Inventors: Shojiro Nakahara;I-Iidetoshi Kurebayshi,

both of Kamakura, Japan [73] Assignee: Mitsubishi Denki KabushlkiKaisha,

Tokyo, Japan 22 Filed: Feb. 17,1970

21 Appl.No.: 11,939

[1 1 3,670,267 [451 June 13, 1972 3,525,952 8/1970 Siekanowicz et al.......333/24.l X

2,848,688 8/1958 Fraser ..333/l .l X 3,017,585 l/l962 Luke ..333/l0 XOTHER PUBLICATIONS Trwehaft et al, Use of Microwave Ferrite Toroids toEliminate External Magnets and Reduce Twitching Power Proc. of IRE. Aug.1958, Pg. 1538 Wright, Diodes or Ferrites- Which Switch? Microwaves,Dec. 1962 Primary Examiner-Paul L. Gensler Attorney-Robert E. Burns andEmmanuel J. Lobato 57] ABSTRACT Two rectangular waveguides areinterconnected by a coupling aperture in which a ferrimagnetic body isdisposed. At least one latching conductor extends through the body inthe axial direction of the waveguides or in a direction perpendicularthereto. A pulse current flowing through the conductor causes a changein direction or magnitude of the magnetization of the ferrimagneticbody. This permits an electromagnetic wave, applied to either one of theinput waveguide ends, to appear at that output end at which the wave didnot previously appear.

6 Clainu, 11 Drawing Figures 20 SOURCE PA'TENTEDJun 1 3 m2 3.670.267

FIG. I (PRIOR ART) FIG, 2 (PRIOR ART) PHASE CIR um I j T SHIFTER FARADAY4 3 POLARIZATION "3' 3- eflmcums --9 PHASE FILTER SHIFTER T FIG. a FIG.40 FIG. 4

" M ULE Z0 souRcE. A 4- .FI,6 .5' c A 44 nae c MICROWAVE SWITCHUTILIZING LATCI-IED FERRIMAGNETIC MATERIAL IN COUPLING APERTURE OFWAVEGUIDE COUPLER BACKGROUND OF THE INVENTION referred to involve anarrangement including a pair of 90 phase shifters having coupled to theinput and output ends hybrid circuits respectively, an arrangementincluding a Faraday rotator operatively associated with a waveguidepolarization branching filter etc. Such known arrangements have beendisadvantageous in that they are composed of a relatively large numberof components and therefore are inevitably increased not only indimension but also in costs.

SUMMARY OF THE INVENTION Accordingly it is an object of the invention toprovide a new and improved microwave switching device which isrelatively small in dimension and capable of continuously switchingmicrowaves and operating on a low driving power.

It is another object of the invention to provide a microwave switchingdevice of the type as described in the preceding paragraph including aplurality of conductors operatively associated with a body offerrimagnetic material involved and selectively used to be operative inreciprocal mode.

It is a further object of the invention to provide a new and improvedmicrowave switching device not only acting as a switch for completelyswitching one to the other of the associated circuits but also capableof switching from one to the other of the circuits such that theassociated electrical energy is applied in any desired proportion toboth the circuits.

The invention accomplishes the aforesaid objects by the provision of amicrowave switching device for use with a waveguide multi-portcomprising a pair of coupling sections of waveguide interconnected onthe adjacent side walls and having respective input and output ends, anda body of ferrimagnetic material loaded at the junction of the sectionsof waveguide, characterized in that the body of ferrimagnetic materialhas a hole extending therethrough in a selected one of the axialdirections of the waveguide sections, and in a direction perpendicularthereto, a latching conductor extending through the hole, and means forcausing a current to flow through the latching conductor to change themagnitude or direction of magnetization of the body of ferrimagneticmaterial thereby either to switch one to the other of the output endsfor delivering the associated electromagnetic wave or to change amagnitude of an output from the particular output end.

In order to provide a reciprocal switch, the body of ferrimagneticmaterial may have a plurality of holes extending through in a selectedone of the axial direction of the waveguide sections and a directionperpendicular thereto and one latching conductor extends through each ofthe holes, a current being caused to selectively flow through thelatching conductors.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will become more readilyapparent from the following detailed description taken in conjunctionwith the accompanying drawing in which:

FIG. 1 is a schematic circuit diagram of a microwave switching deviceconstructed in accordance with the principles of the prior art;

FIG. 2 is a schematic view of another microwave switching deviceconstructed in accordance with the principles of the prior art;

FIG. 3 is a perspective view of a microwave switching device constructedin accordance with the principles of the invention with parts brokenaway for the purpose of illustrating the internal structure;

FIG. 4a and b are sectional views of a body of ferrimagnetic materialused in the device shown in FIG. 3, and in its differently magnetizedstates;

FIG. 5 is a schematic plan view of the device shown in FIG. 3 useful inexplaining the operation of the invention;

FIG. 6 is a sectional plan view, of the most generic form of theinvention; and

FIGS. 7a and b andFIGS. 8a and b are fragmental views of modificationsof the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS hybrid circuits 1 and a pair ofvariable phase shifters 2 connected in parallel circuit relationshipbetween the hybrid circuits l with one of the hybrid circuits, in thiscase, the lefthand circuit, terminated by a matched dummy load 3. Thephase shifters 2 each are adapted to impart to its output a phase angleof from 0 to or 90 to 0 with respect to its input. In FIG. 2 a Faradayrotator 4 is operatively associated with a waveguide polarizationbranching filter 5. The arrangements as shown in FIGS. 1 and 2 are theconventional microwave switching devices for continuously switchingmicrowaves applied thereto. The details of construction and operationsthereof are well known in the art and need not be further described. Itis sufficient to note that such microwave switching devices have beendisadvantageous in that they are large in dimension, expensive tomanufacture and inconvenient for practical use due to the relativelylarge number of components forming the device.

The invention contemplates to eliminate those disadvantages of theconventional microwave switching devices and will now be described indetail with reference to FIGS. 3, 4 and 5.

FIG. 3 is a perspective view of a device constructed in accordance withthe principles of the invention. The arrangement illustrated comprises apair of similarly oriented rectangular waveguide sections generallydesignated by the reference numeral 10 and interconnected inside-to-side relationship by having the adjacent side walls connectedtogether to form a common side wall portion. The interconnected sidewalls are partly removed to form a coupling aperture 12 resembling instructure a short slot type directional coupler well known in the art. Abody 14 composed of ferrimagnetic material, shown in FIG. 4 as being ofrectangular cross section, is loaded or disposed in the couplingaperture 12 such that its longitudinal axis substantially coincides withthe interface of the connected side walls of the waveguide sections 10.A bore or hole 16 extends centrally through the body 14 of ferrimagneticmaterial in the longitudinal axial direction of the waveguide sections10 and has a latching conductor 18 threaded therethrough. The latchingconductor 18 has both end portions insulatingly extending through theouter side wall of one of the waveguide sections 10 and connected acrossa source 20 of current pulses. A current pulse from the source 20 isadapted to flow through the latching conductor 18 to magnetize theferrimagnetic body 14 or to invert it from one to the other of itsmagnetized states. For example with the ferrimagnetic body 14 put in itsmagnetized state as illustrated in FIG. 4a, a current pulse flowing fromthe source 20 through the conductor 18 can change the body 14 to itsother magnetized state as illustrated in F IG. 4b.

In FIG. 4a, a current is shown as flowing from the source 20 through thelatching conductor 18 in a direction directed to the plane of FIG. 4afrom the rear side thereof, as shown by the conventional symbol dot incircle, to provide a magnetic flux flowing within the ferrimagneticmaterial 14 in the counter clockwise direction as viewed in FIG. 4a. InFIG. 4b, a current is shown as flowing through the conductor 18 in theopposite direction, as shown by the conventional symbol, cross incircle," and therefore the resulting magnetic flux is in the oppositedirection or the clockwise direction as viewed in FIG. 4b.

The operation of the arrangement as illustrated in FIG. 3 will now bedescribed with reference to FIG. 5 wherein the device is shown in topplan view as including terminal pairs labelled with the referencecharacters A, B, C and D at the input and output ends. Anelectromagnetic wave entered into the terminal pair A reaches thecoupling aperture 12 in which it is in the TE and TE modes as willreadily be understood. More specifically, the electromagnetic wave fromthe terminal pair A reaches the coupling aperture 12 and therefore thatend face 22 near to the tenninal pair A of the ferrimagnetic body 14 onwhich the wave is divided into the TE and TE modes of transmission. Thenthe waves in the TE and TE modes travel in that portion loaded by theferrimagnetic body 14 of the coupling aperture 12 to the other end face24 of the body 14. Thus it will be appreciated that the phaserelationship between the TE, and T15 modes of the wave as having reachedthe end face 24 of the ferrimagnetic body 14 determines the amount ofpower emerging from the terminal pairs C and D.

It is apparent that the TE and TE modes of transmission existing in thebody 14 of ferrimagnetic material are different from those existing inan empty waveguide, but what corresponds to each of the transmissionmodes in an empty waveguide portion is present in the ferrimagneticmaterial. Therefore, for purposes of simplicity, the termsTE and TEmodes" are used with respect to that portion loaded by the ferrimagneticmaterial of the coupling aperture.

It is now assumed that the fem'magnetic material 14 is in its magnetizedstate as shown in FIG. 4a. Also it is assumed that the coupling aperture12 is loaded by the ferrimagnetic body 14 substantially throughout thelength thereof along the axial direction of the waveguide sections asshown in FIG. 5. Under the assumed conditions the electromagnetic waveincident upon the terminal pair A will be transmitted only to theterminal pair D provided that the following equation is held:

B phase constant of TE mode on ferrimagnetic material loaded portion,

B phase constant of TE mode on ferrimagnetic material loaded portion,

If length of coupling aperture and therefore of ferrimagnetic body. Thenif a current flows through the latching conductor 18 in a direction assymbolically shown in FIG. 4b the ferrimagnetic body 14 changes from itsmagnetized state as illustrated in FIG. 4a to its magnetizes state asillustrated in FIG. 4b. It is assumed that this change in magnetizedstate causes the phase constants B and B to vary by the amounts of ABand A13 respectively and that the following equation is held:

form= 1,2,.

Then the power is transmitted to the terminal pair C alone. Subtractingthe equation 2 from the equation 1 yields (AB -AB lf=i{2(nm)1}1'r 3.Therefore if the equations 1 and 3 are simultaneously held thenswitching is possible between the terminal pairs C and D. It is notedthat, with the coupling aperture 12 loaded by the ferrimagnetic body 14almost throughout the length thereof as shown in FIG. 5, both equations1 and 3 are not always and simultaneously held. However, if the equation3 is held, the equation I is possible to be held by increasing thelength of the unloaded portion of the coupling aperture 12 or by loadinga body of dielectric material on the coupling aperture 12.

Actually, an impedance matching means is required to be operativelyassociated with the ferrimagnetic body 14 or the abovementioneddielectric body for adjusting the electrical length in order to minimizereflection from the end face of either body. While any one of variousmatching means may be used, the use of a dielectric material will now bedescribed in conjunction with FIG. 6 wherein like reference numeralsdesignate the components corresponding to those shown in FIGS. 3 and 5.

In FIG. 6, the coupling aperture 12 includes an unloaded portion 26 or28 formed at either end. The body 14 of ferrimagnetic material loadingthe coupling aperture 12 is provided on one end face, in this case, thelefthand face as viewed in FIG. 6 with a matching body 30 of dielectricmaterial and on the other end face with a matching body 32 of dielectricmaterial. Also an adjusting body 34 of dielectric material is integrallyattached to the matching dielectric body. It is now assumed that the T5and T5 modes on the unloaded portions 26 or 28 and those parts loadedwith the matching dielectric bodies 30 and 32, the adjusting dielectricbody 34 and ferrimagnetic body 14 of the coupling aperture 12 have theirphase constants of B10! B20 Bldm Bid!!! Bid B2dr B1! and B?!respectively and lengths of la, Idm, Id and If respectively as shown inFIG. 6. Then the equation 1 can be replaced by the equation {(Bla (BldmBMm) dm (Bld Id +(BU B2I') f 4 for n 1,2, Therefore only what isrequired is to determine the lengths la, ldm, Id and If so as to holdthe equation 4.

Then a question rises as to whether or not the arrangement as shown inFIG. 6 will be possible to hold the equation 3. The ferrimagnetic body14 effects changes in the phase constants AB and A3 for the respectivemodes in the similar manner as does the conventional type of latchingphase shifters. These changes in phase constants are caused from achange in effective permeability occur-ing by changing from one to theother of the polarities of magnetization as shown in FIGS. 4a and b. IfA3,, is equal to Afi then the equation (3) is not held. However with thecoupling aperture 12 loaded as shown in FIG. 3 or 6 it is resulted thatthe ferrimagnetic body 14 is disposed at its position where thetransverse field is high for the TE mode and low for the TE mode wherebyit is differently affected by the individual modes. Therefore, AB isgenerally different from AB y. Furthermore, for the TE and TE modestraveling in a common direction the circularly polarized wave componentsof such modes in the portion loaded with ferrimagnetic material areopposite in direction of rotation from each other with the result thatif Afl is greater than zero A13 is smaller than zero and vice versa.Thus the AB and A3,, are effectively added to each other in the equation(3.) This means that the equation 3) can be held with a particularlength of the ferrimagnetic body 14.

Here it is to be noted that the switching device as above described isnot reciprocal for the following reasons: That portion loaded with theferrimagnetic body 14 of the coupling aperture 12 has its phase constantdependent upon the direction in which an electromagnetic wave isincident thereupon. For example, assuming that the phase constants forthe respective modes are of B and B for a electromagnetic wave incidentupon the terminal pair B, their values change to fi -l- AB and B Afi foran electromagnetic wave incident upon the terminal pair D. (If theferrimagnetic material is inversed in polarity of magnetization theabove relationship is also reversed.) Thus when an electromagnetic wavehas been applied to the terminal pair D such that the electromagneticwave falling upon the terminal pair A emerges from the terminal pair D,the wave emerges from the terminal pair B rather than from the tenninalpair A. In other words, the fixing of the polarity of magnetization ofthe ferrimagnetic material provides one kind of circulator.

In the arrangement as above described, an electromagnetic wave scarcelyemerges from that terminal pair disposed adjacent the particularterminal pair to which the wave is applied. For example, with the waveapplied to the terminal pair A, it scarcely emerges from the terminalpair B. However under these circumstances the wave will actually emergefrom the terminal pair B due to some leakage between the adjacentterminal pairs. Therefore if the arrangement is utilized as a singlethrow double pole switch, the particular terminal pair not required isterminated by a matched dummy load.

While the invention has been illustrated and described in conjunctionwith a switch having a non-reciprocal characteristic, is to beunderstood that it is equally applicable to reciprocal switches. To thisend, the ferrimagnetic body 14 as shown in FIG. 3 or 6 can be replacedby a body of ferrimagnetic material capable of realizing any one of itsmagnetized states such as shown in FIG. 7. The ferrimagnetic members orbodies 14 each are shown in FIG. 7 as including a plurality of crossholes 16 in this case, three, extending therethrough in a directionperpendicular to the longitudinal axial direction of the associatedwaveguide sections (not shown) and a pair of parallel holes 16extendingtherethrough in thelongitudinal axial direction of thewaveguide section (not shown). Then one latching conductor 18 isthreaded through each of the holes 16. If desired, a single crossconductor 18 may be used. Pulse currents can flow through the respectivelatching conductors 18 in the direction symbolically shown in FIG. 7 toput the associated ferrimagnetic body 14 in the magnetized statereversed from that shown at the arrow in FIG. 7a or 7b. Theferrimagnetic body 14 may be put in its magnetized state of oppositepolarity in the cross sectional plane as shown in FIG., 7a and it may beput in its magnetized state of one or the other polarity in thelongitudinal sectional plane as shown in FIG. 7b. The ferrimagnetic body14 as shown in FIG. 7 can replace the ferrimagnetic body 14 in thearrangement as shown in FIG. 3 or 6 to provide a reciprocal switch.

While the device is in any one of the magnetized state of theferrimagnetic body 14 as shown in FIG. 7, a pulse current can flowthrough the latching conductors in a direction opposite to thatsymbolically shown in FIG. 7 to change the ferrimagnetic body 14 to itsmagnetized state reversed from that illustrated. Since the ferrimagneticmaterial has its effective permeabilities for TE and TE modes dependentupon its magnetized state, changing one to the other of its magnetizedstate causes a change in phase constant for each mode. Thus it will beappreciated that such a reciprocal switching device is operative in thesubstantially identical manner as previously described in conjunctionwith the non-reciprocal devices.

The dimension of the ferrimagnetic body 14 can be properly chosen tohold the equations (3) and (4) providing a reciprocal switch. In thereciprocal switches it is noted that unlike the non-reciprocal switchesa change in magnetized state does not cause AB and A13 to vary in sign.In other words, the efiective permeability is not affected by thedirection of rotation of the circularly polarized wave. Therefore adifference between A3,, and Afl is caused only from a difference indistribution of the electromagnetic field between the TE and T modes.This result in the necessity of increasing the required length of theferrimagnetic body as compared with the non-reciprocal arrangements.

While the invention has been illustrated and described in terms of thecase complete switching is efiected between the terminal pairs C and Dit is to be understood that the invention is equally applicable to thecase partial switching is effected to cause an electromagnetic wave toappear in both the adjacent terminal pairs with any desired proportionof its energies. Such partial switching is accomplished by properlyselecting the values of the righthand sides of the equations 3 and 4.For example, the dimension of the ferrimagnetic body 14 may be selectedto render the righthand side of the equation '3 equal to 1r/4 while theequation 4 is left intact. Under these circumstances, thatelectromagnetic wave emerging only from the terminal pair D in themagnetized state of the ferrimagnetic body 14 as shown in FIG. 4aresponds to a change to the magnetized state of the body as shown inFIG. 4b to be divided into two equal portions emerging from both theterminal pairs C and D respectively.

Also the invention has been described in conjunction with a change indirection of a pulse current flowing through the latching conductor orconductors to change the ferrimagnetic body from one to the other of itsmagnetized states. However his to be understood that according to theprinciples of the inamount of power emerging from the particularterminal pair. This is because a change in magnitude of the currentcauses a variation in magnitude of magnetization of the ferrimagneticmaterial leading to changes in the AB and Afi thereof.

The invention has several advantages. For example, it is simple inconstruction and small-sized. Also, a pulse current is required onlywhen the ferrimagnetic body is to be changed from one to the othermagnetized state and no power is required to maintain the ferrimagneticbody in either of its magnetized states thereby resulting in a lowdriving power.

What we claim is:

l. A microwave switching device for use with a waveguide multi-portcomprising, in combination: a pair of coupling sections of waveguideinterconnected along a common side wall and having respective input andoutput ends, means defining a coupling aperture in said common sidewall, a body of ferrimagnetic material disposed within said couplingaperture, said body of ferrimagnetic material having means thereindefining a plurality of holes extending therethrough in the longitudinalaxial direction of the waveguide sections and means therein defining aplurality of holes extending therethrough in a direction perpendicularto said longitudinal axial direction, a latching conductor extendingthrough each of said holes, and means for causing a current to flowthrough said latching conductor to selectively change the direction ofmagnetization of said body of ferrimagnetic material to thereby switchone to the other of said output ends for delivering therethrough anelectromagnetic wave received at one of said input ends.

2. A microwave switching device as claimed in claim 1 whereinsaidcoupling aperture contains therein a matching body of dielectricmaterial.

3. A microwave switching device for use with a waveguide multi-portcomprising, in combination: a pair of coupling sections of waveguideinterconnected along a common side wall and having respective input andoutput ends, means defining a coupling aperture in said common sidewall, a body of ferrimagnetic material disposedwithin said couplingaperture, said body of ferrimagnetic material having means thereindefining a plurality of holes extending therethrough in the longitudinalaxial direction of the waveguide sections and means therein defining aplurality of holes extending therethrough in a direction perpendicularto said longitudinal axial direction, a latching conductor extendingthrough each of said holes, and means for causing suflicient current toflow through said latching conductor to change the magnitude ofmagnetization of said body of ferrimagnetic material to thereby changethe magnitude of an output from the particular output end.

4. A microwave switching device as claimed in claim 3 wherein saidcoupling aperture contains therein a matching body of dielectricmaterial.

5. A microwave switch comprising: a pair of similarly orientatedwaveguide sections each having an input end and an output end axiallyspaced apart from each other along a longitudinal axis of the waveguidesection; means connecting together said pair of waveguide sections inside-by-side relationship including'a common side wall portion common toboth said waveguide sections; means defining only a single couplingaperture in said common side wall portion coupling together said pair ofwaveguide sections; a ferrimagnetic member disposed within said singlecoupling aperture; and means coacting with said ferrimagnetic member forselectively developing a magnetic field of sufficient strength andpolarity to effectively switch the path of travel of an electromagneticwave received at one input end of one waveguide section between eachoutput end of said pair of waveguide sections, said last-mentioned meanscomprising means defining at least one hole extending through saidferrimagnetic member in a direction parallel to the longitudinal axis ofsaid waveguide sections, means defining at least one other holeextending said ferrimagnetic member in a direction perpendicular to saidlongitudinal axis, a latching conductor threaded through each of saidholes, and means for selectively flowing current through vention a pulsecurrent may vary in magnitude to change 11 said latching conductor todevelop said magnetic field.

6. A switch according to claim 5; wherein said ferrimagnetic member hasplanar side walls and planar end faces and is symmetrically disposed insaid coupling aperture with respect to said pair of waveguide sections.

1. A microwave switching device for use with a waveguide multiportcomprising, in combination: a pair of coupling sections of waveguideinterconnected along a common side wall and having respective input andoutput ends, means defining a coupling aperture in said common sidewall, a body of ferrimagnetic material disposed within said couplingaperture, said body of ferrimagnetic material having means thereindefining a plurality of holes extending therethrough in the longitudinalaxial direction of the waveguide sections and means therein defining aplurality of holes extending therethrough in a direction perpendicularto said longitudinal axial direction, a latching conductor extendingthrough each of said holes, and means for causing a current to flowthrough said latching conductor to selectively change the direction ofmagnetization of said body of ferrimagnetic material to thereby switchone to the other of said output ends for delivering therethrough anelectromagnetic wave received at one of said input ends.
 2. A microwaveswitching device as claimed in claim 1 wherein said coupling aperturecontains therein a matching body of dielectric material.
 3. A microwaveswitching device for use with a waveguide multi-port comprising, incombination: a pair of coupling sections of waveguide interconnectedalong a common side wall and having respective input and output ends,means defining a coupling aperture in said common side wall, a body offerrimagnetic material disposed within said coupling aperture, said bodyof ferrimagnetic material having means therein defining a plurality ofholes extending therethrough in the longitudinal axial direction of thewaveguide sections and means therein defining a plurality of holesextending therethrough in a direction perpendicular to said longitudinalaxial direction, a latching conductor extending through each of saidholes, and means for causing sufficient current to flow through saidlatching conductor to change the magnitude of magnetization of said bodyof ferrimagnetic material to thereby change the magnitude of an outputfrom the particular output end.
 4. A microwave switching device asclaimed in claim 3 wherein said coupling aperture contains therein amatching body of dielectric material.
 5. A microwave switch comprising:a pair of similarly orientated waveguide sections each having an inputend and an output end axially spaced apart from each other along alongitudinal axis of the waveguide section; means connecting togethersaid pair of waveguide sections in side-by-side relationship including acommon side wall portion common to both said waveguide sections; meansdefining only a single coupling aperture in said common side wallportion coupling together said pair of waveguide sections; aferrimagnetic member disposed within said single coupling aperture; andmeans coacting with said ferrimagnetic member for selectively developinga magnetic field of sufficient strength and polarity to effectivelyswitch the path of travel of an electromagnetic wave received at oneinput end of one waveguide section between each output end of said pairof waveguide sections, said last-mentioned means comprising meansdefining at least one hole extending through said ferrimagnetic memberin a direction parallel to the longitudinal axis of said waveguidesections, means defining at least one other hole extending saidferrimagnetic member in a direction perpendicular to said longitudinalaxis, a latching conductor threaded through each of said holes, andmeans for selectively flowing current through said latching conductor todevelop said magnetic field.
 6. A switch according to claim 5; whereinsaid ferrimagnetic member has planar side walls and planar end faces andis symmetricalLy disposed in said coupling aperture with respect to saidpair of waveguide sections.